This invention relates to a power converter comprising controlled rectifiers for supplying electric power to a D.C. load such as a D.C. motor, and more particularly to a universal power converter which can operate with both a D.C. power source and an A.C. power source.
Prior art power converters used in conjunction with a power source for supplying electric power to a D.C. load such as a D.C. motor are classified into two types depending on whether the power source is a D.C. power supply or an A.C. power supply. That is, a power converter unit such as a chopper is employed for the desired D.C. - D.C. conversion when the power source is a D.C. power supply, and a power converter unit of the kind comprising a bridge connection of controlled rectifiers is employed for the desired A.C. - D.C. conversion when the power source is an A.C. power supply.
Thus, it has been common practice to design and construct power converters for exclusive use with either a D.C. power source or an A.C. power source, and it has been necessary to prepare a power converter consisting of a D.C. - D.C. power converter unit and an A.C. - D.C. power converter unit and to selectively place such converter units in operation in an A.C. - D.C. dual-service electric car which is adapted to run in both a D.C. powered section and an A.C. powered section of an electrified railway system. Therefore, the prior art power converter has been defective in that not only the overall size and weight thereof are considerably large but also the manufacturing cost thereof is considerably high.
Recently, an A.C. - D.C. dual-service electric car is strongly demanded which can singly run in both an A.C. powered section and a D.C. powered section of an electrified railway system under both a power running condition and a regenerative braking condition.